// Copyright (C) Kumo inc. and its affiliates.
// Author: Jeff.li lijippy@163.com
// All rights reserved.
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
//
#pragma once

#include <boost/random/uniform_01.hpp>
#include <pollux/testing/expression/decimal_arg_types_generator_base.h>

namespace kumo::pollux::exec::test {

class TruncateArgTypesGenerator : public fuzzer::ArgTypesGenerator {
 public:
  std::vector<TypePtr> generateArgs(
      const exec::FunctionSignature& signature,
      const TypePtr& returnType,
      FuzzerGenerator& rng) override {
    // Only the single-arg truncate function is supported because
    // ArgumentTypeFuzzer can generate argument types for the two-arg truncate
    // function.
    POLLUX_CHECK_EQ(1, signature.argumentTypes().size());
    // Generates a decimal type following below formulas:
    // p = max(p1 - s1, 1)
    // s = 0
    const auto [p, s] = getDecimalPrecisionScale(*returnType);
    if (s != 0) {
      return {};
    }

    // p1 = s1
    if (p == 1 && coinToss(rng)) {
      const auto s1 = rand32(1, 38, rng);
      return {DECIMAL(s1, s1)};
    }

    const auto s1 = rand32(0, 38 - p, rng);
    return {DECIMAL(p + s1, s1)};
  }

 private:
  // Returns true 50% of times.
  static bool coinToss(FuzzerGenerator& rng) {
    return boost::random::uniform_01<double>()(rng) < 0.5;
  }

  static uint32_t rand32(uint32_t min, uint32_t max, FuzzerGenerator& rng) {
    return boost::random::uniform_int_distribution<uint32_t>(min, max)(rng);
  }
};

} // namespace kumo::pollux::exec::test
